scripts: check-variable-fonts.sh: convert to Python

This script handle errors when trying to build translations
with make pdfdocs.

As part of our cleanup work to remove hacks from docs Makefile,
convert this to python, preparing it to be part of a library
to be called by sphinx-build-wrapper.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Message-ID: <d438fb01d2c00e2c2b4ac16f999d9a8ce848251b.1758196090.git.mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

3 files changed, 79 insertions, 29 deletions

diff --git a/Documentation/Makefile b/Documentation/Makefile
index 3609cb86137b..8dca118e9520 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -149,7 +149,7 @@ pdfdocs: DENY_VF = XDG_CONFIG_HOME=$(FONTS_CONF_DENY_VF)
 pdfdocs: latexdocs
 	@$(srctree)/scripts/sphinx-pre-install --version-check
 	$(foreach var,$(SPHINXDIRS), \
-	   $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" $(DENY_VF) -C $(BUILDDIR)/$(var)/latex || sh $(srctree)/scripts/check-variable-fonts.sh || exit; \
+	   $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" $(DENY_VF) -C $(BUILDDIR)/$(var)/latex || $(PYTHON3) $(srctree)/scripts/check-variable-fonts.py || exit; \
 	   mkdir -p $(BUILDDIR)/$(var)/pdf; \
 	   mv $(subst .tex,.pdf,$(wildcard $(BUILDDIR)/$(var)/latex/*.tex)) $(BUILDDIR)/$(var)/pdf/; \
 	)
diff --git a/MAINTAINERS b/MAINTAINERS
index ac47a5d0d8e8..b0e9b793519f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7301,7 +7301,7 @@ S:	Maintained
 P:	Documentation/doc-guide/maintainer-profile.rst
 T:	git git://git.lwn.net/linux.git docs-next
 F:	Documentation/
-F:	scripts/check-variable-fonts.sh
+F:	scripts/check-variable-fonts.py
 F:	scripts/checktransupdate.py
 F:	scripts/documentation-file-ref-check
 F:	scripts/get_abi.py
diff --git a/scripts/check-variable-fonts.sh b/scripts/check-variable-fonts.py
index ce63f0acea5f..8be1c0f39588 100755
--- a/scripts/check-variable-fonts.sh
+++ b/scripts/check-variable-fonts.py
@@ -1,7 +1,9 @@
-#!/bin/sh
+#!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0-only
 # Copyright (C) Akira Yokosawa, 2024
 #
+# Ported to Python by (c) Mauro Carvalho Chehab, 2025
+#
 # For "make pdfdocs", reports of build errors of translations.pdf started
 # arriving early 2024 [1, 2].  It turned out that Fedora and openSUSE
 # tumbleweed have started deploying variable-font [3] format of "Noto CJK"
@@ -87,29 +89,77 @@
 #     Denylisting should be less invasive, as it is effective only while
 #     XeLaTeX runs in "make pdfdocs".
 
-# Default per-user fontconfig path (overridden by env variable)
-: ${FONTS_CONF_DENY_VF:=$HOME/deny-vf}
-
-export XDG_CONFIG_HOME=${FONTS_CONF_DENY_VF}
-
-notocjkvffonts=`fc-list : file family variable | \
-		grep 'variable=True' | \
-		grep -E -e 'Noto (Sans|Sans Mono|Serif) CJK' | \
-		sed -e 's/^/    /' -e 's/: Noto S.*$//' | sort | uniq`
-
-if [ "x$notocjkvffonts" != "x" ] ; then
-	echo '============================================================================='
-	echo 'XeTeX is confused by "variable font" files listed below:'
-	echo "$notocjkvffonts"
-	echo
-	echo 'For CJK pages in PDF, they need to be hidden from XeTeX by denylisting.'
-	echo 'Or, CJK pages can be skipped by uninstalling texlive-xecjk.'
-	echo
-	echo 'For more info on denylisting, other options, and variable font, see header'
-	echo 'comments of scripts/check-variable-fonts.sh.'
-	echo '============================================================================='
-fi
-
-# As this script is invoked from Makefile's error path, always error exit
-# regardless of whether any variable font is discovered or not.
-exit 1
+import os
+import re
+import subprocess
+import sys
+import textwrap
+
+class LatexFontChecker:
+    """
+    Detect problems with CJK variable fonts that affect PDF builds for
+    translations.
+    """
+
+    def __init__(self):
+        deny_vf = os.environ.get('FONTS_CONF_DENY_VF', "~/deny-vf")
+
+        self.environ = os.environ.copy()
+        self.environ['XDG_CONFIG_HOME'] = os.path.expanduser(deny_vf)
+
+        self.re_cjk = re.compile(r"([^:]+):\s*Noto\s+(Sans|Sans Mono|Serif) CJK")
+
+    def get_noto_cjk_vf_fonts(self):
+        """Get Noto CJK fonts"""
+
+        cjk_fonts = set()
+        cmd = ["fc-list", ":", "file", "family", "variable"]
+        try:
+            result = subprocess.run(cmd,stdout=subprocess.PIPE,
+                                    stderr=subprocess.PIPE,
+                                    universal_newlines=True,
+                                    env=self.environ,
+                                    check=True)
+
+        except subprocess.CalledProcessError as exc:
+            sys.exit(f"Error running fc-list: {repr(exc)}")
+
+        for line in result.stdout.splitlines():
+            if 'variable=True' not in line:
+                continue
+
+            match = self.re_cjk.search(line)
+            if match:
+                cjk_fonts.add(match.group(1))
+
+        return sorted(cjk_fonts)
+
+    def check(self):
+        """Check for problems with CJK fonts"""
+
+        fonts = textwrap.indent("\n".join(self.get_noto_cjk_vf_fonts()), "    ")
+        if not fonts:
+            return None
+
+        rel_file = os.path.relpath(__file__, os.getcwd())
+
+        msg = "=" * 77 + "\n"
+        msg += 'XeTeX is confused by "variable font" files listed below:\n'
+        msg += fonts + "\n"
+        msg += textwrap.dedent(f"""
+                For CJK pages in PDF, they need to be hidden from XeTeX by denylisting.
+                Or, CJK pages can be skipped by uninstalling texlive-xecjk.
+
+                For more info on denylisting, other options, and variable font, see header
+                comments of {rel_file}.
+            """)
+        msg += "=" * 77
+
+        return msg
+
+if __name__ == "__main__":
+    msg = LatexFontChecker().check()
+    if msg:
+        print(msg)
+
+    sys.exit(1)